I. Field of the Invention
The invention relates to burner assemblies and, more particularly, to burner assemblies used in lamps, decorative lighting devices and the like and having a plastic fuel container or canister.
Burner assemblies for lamps, decorative lighting devices and the like typically include a canister containing liquid fuel and having a raised neck forming an opening through which fuel is introduced into the canister and a cap for holding a wick and covering the canister. The cap typically is stamped from a metal and the canister typically is molded from a plastic material.
II. Description of the Prior Art
In one type of burner assembly, the cap has a raised central portion for holding a wick and a peripheral collar which fits over the rim of the canister neck and is crimped underneath a radially outwardly extending lip on the canister neck to form a seal and lock the cap in place on the canister. Representative prior art patents disclosing such an arrangement include U.S. Giangiulio Pat. No. 4,025,290, U.S. Menten Pat. No. 4,805,076 and U.S. Tendick Pat. No. 4,892,711.
The metal caps of some of these constructions can transfer heat from a burning wick to the plastic material in the region of the rim of the canister neck. The plastic material can soften and cause the seal between the canister neck and the cap collar to be broken. When this occurs, the liquid fuel can leak past the collar any time the canister is tipped over or jostled.
U.S. Thompson Pat. No. 5,000,678 discloses a cap construction which is designed to alleviate this and other shortcomings associated with prior arrangements. In this construction, the cap includes an annular, peripheral collar which fits over the outer lip of the canister neck. The cap includes an annular inner flange which fits snugly inside the canister neck so that, when the collar is crimped over the outer lip on the canister neck, the upper part of the canister neck is sandwiched between the outer collar and the inner flange.
In all the above constructions, the metal cap is permanently affixed to the canister. Thus, the canister cannot be refilled with fuel and, instead, the entire burner assembly is discarded after all the fuel has been used. It is known to use a one-piece wick holder which is removably mounted on a refillable plastic canister by providing mating threads on the wick holder and the canister. Because of the heat transferred from a burning wick to the plastic material in the region of the threads via the metal wick holder, the plastic material softens, causing the threads to lose their original shape and the threads tend not to return to their original shape upon cooling. Consequently, after several softening and cooling cycles during use, the shape of the threads can change enough to prevent the wick holder from being suitably affixed to the canister after it has been removed for refilling the canister.
U.S. Olsen Pat. No. 4,728,286 discloses a lamp including a base, a disposable fuel container having a rupturable cover which is press fitted inside an opening in the container and a wick support removably mounted on the container cover. The cover includes three circumferentially spaced projections which snap over a neck surrounding the container opening. Thus, in addition to the container not being refillable, there is no external means on either the container or the wick support to assist in preventing the container neck from being misshapened by heat transferred from a burning wick.